Silane compounds having a norbornyl radical are useful as reactants for various silicone compounds (for use in paint, adhesives, and high refractive index materials), coupling agents, coating composition ingredients, and organic synthesis intermediates. While norbornyl-containing compounds are known to have a high refractive index and thus used in high refractive index materials, they are still insufficient in refractive index. While a compound having a higher refractive index is desired, there is a need for a silane compound having a linkage of two norbornyl radicals.
For example, Patent Document 1 discloses a method for preparing a vinyl-containing [3-(2-norbornyl)-2-norbornyl]silane compound by reacting 5-vinyl-2-norbornene with a hydrosilane compound in the presence of metallic palladium or a palladium complex containing no phosphorus compound as a ligand.
It is known from Non-Patent Document 1 that a silane compound having a linkage of two unsubstituted norbornyl radicals, typically [3-(2-norbornyl)-2-norbornyl]trichlorosilane is formed as a by-product in hydrosilylation reaction between 2-norbornene and trichlorosilane in the presence of an isopropanol solution of chloroplatinic acid as a catalyst.
However, the vinyl-containing [3-(2-norbornyl)-2-norbornyl]silane compound is not suitable as a reactant for forming coatings on electronic parts. When the compound is subjected to hydrolysis and formulated in a silicone coating composition, the composition can be colored with time due to oxidation of vinyl in the molecule.
While a silicone oil as a high refractive index material ingredient is formed by co-hydrolysis of a silane compound having a linkage of two norbornyl radicals, for example, [3-(2-norbornyl)-2-norbornyl]trichlorosilane and another silane compound, the amount of the trichlorosilane (which is trifunctional) added must be limited in order that the resulting compound remain oily. There is thus a need for a difunctional silane compound having a linkage of two norbornyl radicals, for example, [3-(2-norbornyl)-2-norbornyl]organodichlorosilane which can be added in a higher proportion without depriving the product of oiliness. Also, for use as coupling agent after hydrolysis, a silane compound having a linkage of two norbornyl radicals, for example, [3-(2-norbornyl)-2-norbornyl]organoxysilane is desirable because no corrosive hydrogen chloride is formed as by-product.
Accordingly, it is desirable to have a difunctional silane compound having a linkage of two norbornyl radicals and free of an aliphatic unsaturated radical such as vinyl or an organoxysilane compound having a [3-(2-norbornyl)-2-norbornyl] radical. It is also desirable to have a method for preparing [3-(2-norbornyl)-2-norbornyl]trichlorosilane in high yields.